One of the sources of error in communications links consisting of multiple wires (i.e., multi-wire communications links, or multi-wire communications systems more generally) is crosstalk between the wires. Crosstalk is the coupling of energy from one line to another when one wire transitions from one state to another. Such a transition can have an inductive or a capacitive crosstalk effect on the neighboring wires. Accordingly, the two forms of crosstalk are called inductive and capacitive crosstalk. Inductive crosstalk is caused by coupling of the magnetic fields of the wires, whereas capacitive crosstalk is caused by coupling of the electric fields.
Wires in a communication link are transmission lines, which may be modeled as distributed networks of series inductances and parallel capacitances. Inductive crosstalk as illustrated in FIG. 9A is caused by mutual inductance Lm between the distributed inductances of driven wire 950 and “victim” wire 960. A current through the driven conductor causes a current ILM in the opposite direction in the victim conductor. The strength of this current depends on the derivative of the transition change and the mutual inductance between the wires.
Capacitive crosstalk as illustrated in FIG. 9B is caused by mutual capacitance Cm between driven wire 950 and victim wire 960. Changes in the voltage between conductors results in a current ICM proportional to the rate of the change and the mutual capacitance between the conductors. Thus, the induction process induces a current that flows in the direction opposite to the direction of the original signal transition, while the capacitive process induces current that moves in both directions.